A fuel injector, which has a stepped spray-discharge opening, is discussed in GB 1,088,666 A. The spray-discharge opening is implemented originating from a chamber-shaped valve interior space into a first opening section having a very small opening width, which determines the flow rate, while an adjoining second opening section is significantly expanded. The second opening section may be designed to expand into either a cylinder or a cone. The spray-discharge openings are introduced using conventional technology, such as drilling, milling, embossing, or eroding.
A fuel injector having a valve needle manufactured using the so-called metal injection molding method (MIM method) is also discussed in DE 42 30 376 C1. For the valve needle, a tubular actuating part, which includes an armature section and a valve sleeve section, is produced by injection molding and subsequent sintering. The actuating part is subsequently bonded to a valve closing element section using a welded joint, so that the valve needle is composed of only two individual components. A continuous internal longitudinal opening is provided in the armature section and the valve sleeve section, in which fuel may flow in the direction of the valve closing element section and then exits from the valve sleeve section through transverse openings in the proximity of the valve closing element section. Therefore, slide molds are necessary when manufacturing the valve needle using the MIM method to form the transverse openings.
A binary binder system like the solid polymer solution for the metal injection molding technique is discussed in DE 40 33 952 C1. It is distinguished by the use of physiologically harmless low-molecular binder components and by dispensing with wetting agents. In this way, dense molded parts made of metal powders may be manufactured without problems by injection molding and the binder may be removed therefrom, without contraction or warping.